Electric discharge devices



United States Patent ELECTRIC DISCHARGE DEVICES Walter William Wright, John Arundel Smyth, and Bernard Douglas Mills, London, England, assignors to International Standard Electric Corporation, New York, N. Y.

Application August 3, 1953, Serial No. 371,928

Claims priority, application Great Britain August 22, 1952 2 Claims. (Cl. 313-260) This invention relates to electric discharge devices in which tubular electrodes are mounted.

It is already known to mount a tubular electrode in an insulator by inserting a split mandrel having projections on its surface in the tube and then expanding the mandrel to produce similar projections on the surface of the electrode.

With the reduction of components to miniature size, tubular electrodes are used having so small a cross section that it is impossible to produce locking projections by the above described method.

The object of the present invention is to provide a method by which the necessary projections may be more easily produced, even in tubular electrodes of the size required for miniature electric discharge devices.

According to the present invention there is provided an electric discharge device comprising a tubular electrode having indentations therein and bulges immediately adjacent to said indentations, the said tubular electrode being mounted on an insulator and locked thereto by said bulges being above and below the insulator.

Embodiments of the invention will now be described with reference to the accompanying drawing in which:

Fig. 1 show a side elevation of a tubular cathode mounted in an insulator,

Fig. 2 shows an enlarged cross section through the mounting projections shown in Fig. 1 and the mandrel required for producing the projections and,

Fig. 3 shows an enlarged cross section through an arrangement using another form of mandrel.

Referring to Fig. 1, a tubular cathode 1 is shown mounted in an insulator 2 by means of projections 3, 4, 5 and 6 in the surface of the cathode on either side of the insulator 2. The cathode 1 is passed through a hole in the insulator 2 and then pressure is applied by an external tool to portions 7, 8, 9 and 10. Inside the cathode 1 there is a mandrel shaped to allow indentations to be made at 7, 8, 9 and 10 by the pressure of the tool. This pressing action causes the cathode to bulge out, and the bulging is controlled by the shape of the face of the tool which clamps against the electrode but which is recessed to allow the bulges to form projections at 3, 4, 5 and 6 and so grip the insulator 2 firmly.

Fig. 2 depicts a cross section through the locking projections 3 and 5 of Fig. 1. The hole through the insulator is shown by the line 11 which also defines the original cross section of the cathode. A solid grooved mandrel 12 is shown within the cathode. When pressure is 2,854,601 Patented Sept. 30, 1958 applied by a tool at points 13, 14, 15 and 16 indentations are caused but the cathode is allowed to bulge at 17 and 18 so that it spills over the edge of the insulator bounded by the line 11 and since this operation is performed both above and below the insulator the cathode is mounted firmly in the insulator by these projections.

Fig. 3 shows a cross section through an alternative arrangement where the hole in the insulator and the original cathode section are shown by line 19. A suitably grooved mandrel 20 is inserted in the cathode and pressure is applied at 21, 22, 23, and 24 by a tool which is so shaped as to allow the cathode to bulge out and form projections at points 25, 26, 27 and 28 only. Similar bulges are produced above and below the insulator and so the cathode is firmly mounted in the insulator.

The shape and position of these projections may also be controlled by a die clamped around the cathode.

During this process the electrode is supported both internally and externally and is therefore less liable to distortion. It is also possible to form comparatively small mount projections which can be arranged not to be on the major faces of the electrode so that other electrodes may be placed close to the major faces of the electrode with less danger of contact between the electrodes.

While the principles of the invention have been described above in connection with specific embodiments, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What we claim is: I

1. In a discharge device, an insulator support, a tubular electrode mounted in said insulator, said tubular electrode having a plurality of opposed, longitudinal indentations spaced symmetrically around its periphery, said indentations being spaced from each other by flat, parallel intermediate sections of the tubular electrode, and opposed, arcuate bulges forming longitudinal end sections in said tubular electrode closely adjacent said longitudinal indentations, said bulges providing locking projections on opposing sides of said electrode for locking it to and above and below said insulator.

2. A method of mounting a tubular electrode of an electric discharge device on an insulator, which comprises the steps of inserting said tubular electrode in said insulator, forcing a mandrel with longitudinal grooves into the tubular electrode to indent the electrode longitudinally and peripherally on opposing sides thereof, and pressing portions of the electrodes into the mandrel grooves to form a series of spaced longitudinal projecting bulges on the electrode, adjacent to said indentations, said bulges and indentations being above and below the edges of the insulator for locking both together.

References Cited in the file of this patent UNITED STATES PATENTS 1,935,719 Kayko Nov. 21, 1933 2,063,188 Parker et al. Dec. 8, 1936 2,286,996 Dickinson June 16, 1942 2,507,979 Kelar May 16, 1950 2,679,612 Weiss May 25, 1954 

